1. Field
The following description relates to an electrochromic device including a carbon-based material and a viologen-based compound, a method for producing the electrochromic device, and use thereof.
2. Description of Related Art
Recent research efforts on electrochromic behaviors used in electro-optic applications have focused on developing novel electrochromes and advancing the forms of devices. An important factor in enhancing the performance of electrochromic devices (ECDs) is to greatly increase the electrochrome stability, allowing them to undergo many reversible color changes under applied voltages, and thus, to remain operable over long periods of use. Inorganic electrochromic devices composed of metal oxides have achieved enhanced device performance through structural modifications of electrochromes, development of new dopants, and chemical modifications to the electrode material. For future ECDs, nonetheless, further developments of organic electrochromes are in demand to allow devices to be highly flexible and wearable. However, until now, there have been only a few studies on polymer electrochromes for use in organic electrochromic devices, due to lack of organic monomers that can demonstrate long-term performance under an electric voltage. Therefore, inexpensive, long-lasting, and easily processable organic electrochromes should be investigated intensively for future electro-optic devices.
In an ECD, an electrolyte supports the electrochromic reactions between the two electrodes. Generally, electrolytes are composed of liquid solvents and any of a variety of ionic salts. Metal cations are often combined with a volatile organic solvent in the electrolyte layer, which serves as an ion conducting medium. However, the use of such electrolytes with electrochromes in an ECD system poses the risk of decomposing the metal-ion-containing electrochromes at high voltages, leading to poor ECD stability and eventual performance degradation. Therefore, the durability and the performance of the electrolytes used in ECD systems should be improved to enable future applications such as electrochromic smart windows, displays, and mirrors. Furthermore, in the electrochromic systems, directly combining an electrochromic material with polymer electrolytes or electrodes has been developed. For example, an electrochromic material directly bonded to an electrolyte may produce a somewhat stable electrochromic platform. However, the highly dense polymer used in this platform may decrease its switching properties and coloration efficiency, and also may make the platform unsuitable for flexible applications. In order to realize various electro-optic devices, therefore, it will be necessary to improve the structural combinations of electrolytes, electrochromes, and electrodes. Success in the improvement will enable not only highly stable and structurally simplified ECDs but also highly demanded flexible ECDs.
Meanwhile, Korean Patent Application Publication Nos. 10-2007-0070792 and 10-2014-0001502 describe an electrochromic device including electrolyte.